Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$68.34	4.732%	$71.5738	$71.57	$71.55	$71.60
Purchase #2	$185.33	8.139%	$200.414	$200.41	$200.40	$200.40
Purchase #3	$87.61	4.820%	$91.8328	$91.83	$91.85	$91.80
Purchase #4	$169.85	6.814%	$181.4236	$181.42	$181.40	$181.40
Purchase #5	$235.82	5.577%	$248.9717	$248.97	$248.95	$249.00
Purchase #6	$34.52	10.391%	$38.107	$38.11	$38.10	$38.10
Purchase #7	$42.48	11.318%	$47.2879	$47.29	$47.30	$47.30
7 purchase totals =	$823.95		$879.6108	$879.60	$879.55	$879.60